Mechanisms for resource-directory to resource-directory communications

ABSTRACT

An M2M/IoT resource directory entity may discover and register to other resource directory entities by including criteria attributes in discovery broadcasts and then processing link and metadata that may be included in responses. The resource directory with registrations to other resource directories may service a client request by selecting other resources directories to query based on the request or a query criteria contained therein, and then process link and metadata in responses from the other resource directory entities to aggregate a response to the client. Directory-to-directory registrations may be facilitated via using hierarchical parent-child resource directory identifiers, a peer-to-peer identifier regime, or a combination of the two. Observe notifications may include indicia registrations states, e.g., via change and delete response codes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/431,920 filed Dec. 9, 2016 the disclosure ofwhich is hereby incorporated by reference as if set forth in itsentirety herein.

BACKGROUND

Machine-To-Machine (M2M), Web-of-Things (WoT), and Internet-Of-Things(IoT) network deployments may support M2M/IoT service layers such asoneM2M, ETSI M2M, and OMA LWM2M operating across nodes such as M2M/IoTservers, gateways, and devices which host M2M/IoT applications andservices. Operations of these kinds may include communications asdescribed in, for example, IETF standards for Resource Directory, CoRELink Format, CoAP, and CoAP Observe.

SUMMARY

An M2M/IoT resource directory entity may discover and register to otherresource directory entities by including criteria attributes indiscovery broadcasts and then processing link and metadata that may beincluded in responses. The resource directory with registrations toother resource directories may service a client request by selectingother resources directories to query based on the request or a querycriteria contained therein, and then process link and metadata inresponses from the other resource directory entities to aggregate aresponse to the client. Directory-to-directory registrations may befacilitated via using hierarchical parent-child resource directoryidentifiers, a peer-to-peer identifier regime, or a combination of thetwo. Observe notifications may include indicia registrations states,e.g., via change and delete response codes.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to limitations that solve anyor all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF FIGURES

A more detailed understanding may be had from the following description,given by way of example in conjunction with accompanying drawings.

FIG. 1 shows an example call with message exchanges between a CoAPclient and a CoAP server.

FIG. 2 illustrates the architecture of the CoRE RD.

FIG. 3 shows an example call flow for RD Discovery.

FIG. 4 shows an example call flow for an endpoint registering to an RD.

FIG. 5 shows an example call flow for an endpoint refreshing itsregistration.

FIG. 6 shows an example call flow for registration removal.

FIG. 7 shows an example call flow for a client querying a resource.

FIG. 8 shows an example call flow to observe messages between a CoAPclient and a CoAP server.

FIG. 9 illustrates an example smart city with RDs is deployed in variousgeographic areas.

FIG. 10 illustrates and example of parent-child and peer relationshipsamong various RDs.

FIG. 11 shows an example call flow featuring new and enhanced RD-to-RDcommunications.

FIG. 12 shows an example call flow for an RD Discovery method.

FIG. 13 illustrates example RDID data structures.

FIG. 14 shows an example call flow for an RD-to-RD Registration method.

FIG. 15 shows an example call flow for a failed RD-to-RD registrationresponse followed by a successful registration request using an RDIDprovided in the failed response.

FIG. 16 shows an example call flow for an RD-to-RD Registration updatemethod.

FIG. 17 shows an example call flow for an RD registration removalmethod.

FIG. 18 shows an example call flow for a child RD registering to aparent RD.

FIG. 19 shows an example call flow for a parent RD registering to achild RD.

FIG. 20 shows an example call flow for registration using a partiallyprovisioned RDID.

FIG. 21 shows an example call flow for a registration request without aprovisioned RDID.

FIG. 22 shows an example call flow for a peer-to-peer registrationrequest.

FIG. 23 shows an example call flow of a peer-to-peer registration updatein which the pRDID is provided in the update request.

FIG. 24 shows an example call flow where an RD returns an enhanced RDlookup response which includes another RD's context information wherethe requested resource could be found.

FIG. 25 shows an example call flow of an RD lookup query using ExtendedSearch capability.

FIG. 26 shows an example call flow whereby an RD may initiate anunsolicited request to observe a CoRE link from another RD.

FIG. 27 shows an example call flow where a child RD registers withoutproviding an RDID attribute.

FIG. 28 shows an example call flow for the use of an RD extended search.

FIG. 29 shows an example call flow for an RD extended search that spansmultiple hops.

FIG. 30 shows an example call flow for enhanced observe notifications.

FIG. 31 shows an example graphical user interface for an RD registrationtable.

FIG. 32 is a system diagram of an example machine-to-machine (M2M),Internet of Things (IoT), or Web of Things (WoT) communication system inwhich one or more disclosed embodiments may be implemented.

FIG. 33 is a system diagram of an example architecture that may be usedwithin the M2M/IoT/WoT communications system illustrated in FIG. 32.

FIG. 34 is a system diagram of an example communication network node,such as an M2M/IoT/WoT device, gateway, or server that may be usedwithin the communications system illustrated in FIGS. 32 and 33.

FIG. 35 is a block diagram of an example computing system in which anode of the communication system of FIGS. 32 and 33 may be embodied.

DETAILED DESCRIPTION

An M2M/IoT resource directory entity may discover and register to otherresource directory entities by including criteria attributes indiscovery broadcasts and then processing link and metadata that may beincluded in responses. The resource directory with registrations toother resource directories may service a client request by selectingother resources directories to query based on the request or a querycriteria contained therein, and then process link and metadata inresponses from the other resource directory entities to aggregate aresponse to the client. Directory-to-directory registrations may befacilitated via using hierarchical parent-child resource directoryidentifiers, a peer-to-peer identifier regime, or a combination of thetwo. Observe notifications may include indicia registrations states,e.g., via change and delete response codes.

The goal of a Resource Directory (RD) is to host CoRE Link Formatsrepresenting resources of Internet of Things (IoT) devices and to makethem available to RD clients that may be interested in the resources.These IoT devices may have limited capabilities and have sleeping statesas well. The devices, referred to as “endpoints” in the IETF CoREResource Directory (RD) Internet Draft(draft-ietf-core-resource-directory-07), register their resources asCoRE Link Formats to a registrar RD and a client queries the RD to findthese links.

RD to RD communication may be enabled by defining architecturalstructures wherein RDs are able to communicate with each other either aspeers or in a hierarchy, allowing various approaches to forming flexibleregistrations.

Existing RD Discovery methods may be enhanced to foster RD-to-RDcommunications, e.g., via an RD Identifier (RDID) provisioned to eachRD. The RDID may be included as part of the RD Discovery response. Aquerying RD or an endpoint may select which RD to register to, based onits architectural deployment and RDID.

A new RD Registration may be used to allow RDs to register with eachother. For example, after the completion of RD Discovery, registrationmay proceed in accordance with a peer-to-peer or hierarchical approachto communications.

RD operations may be enhanced via RD-to-RD communications. For example,a querying RD may provide enhanced lookup capabilities to queryingclients by using new RD Query attributes to target and/or limit ExtendedSearches sent to other RDs. Answering RDs may return RD Meta-data in theExtended Search responses to provide additional information about theCoRE Links. In addition, a new enhanced mechanism based on CoAP Observefunctionality may be used to allow endpoints' CoRE Link Formats to becached in RDs other than the registrar RD, without requiring theendpoints to register their resources to multiple RDs to get maximumexposure.

New CoRE Link attributes may be added to support RD-to-RDcommunications. New RD Query attributes and RD Meta-data may be added toenable enhanced RD lookups. For example, a resource directory query or aresource directory discovery request may be qualified by the use ofattributes such as a resource directory identifier (e.g., for a specificresource directory), a qualifier of resource directory identifiers(e.g., to identify class, hierarchical level, or parental or peerrelationship), a limit on the number of resource directories queried, aresponse time requirement, a geo-fence area, a set of GPS coordinates, aregistration lifetime cutoff, an endpoint awake requirement, a loadingcapacity, a cache availability requirement, and a remaining lifetimerequirement.

The current IETF RD draft lacks a mechanism for RDs to communicate witheach other. As a result, client queries to an RD will only generateresults limited to the CoRE Links that are hosted on that particular RD.In an IoT world, which is forecasted to include billions of devices,this limitation constrains an RD's ability to locate IoT resource linksresiding on other RDs. End devices also suffer from a lack of exposureto their resource links due to the limited reach of the RD.

An RD's inability to communicate with other RDs thus places anunnecessary burden on RD clients and endpoints. A client may need toperform multiple discoveries and queries to find all the resource linksit is looking for. Endpoints currently need to register to multiple RDsto achieve maximum exposure of its resource links. These limitations maybe addressed using the RD-to-RD communications methods described herein.

TABLE 1 Acronyms ACK Acknowledgement (CoAP message) CoAP ConstrainedApplication Protocol CON Confirmable (CoAP message) CoRE ConstrainedRESTful Environments ct Content Type (CoRE Link Format attribute) DNSDomain Name System DNS-SD Domain Name System-Service Discovery EPEndpoint et Endpoint Type (CoRE Link Format attribute) FQDN FullyQualified Domain Name GPS Global Positioning System HTTP HypertextTransport Protocol ID Identification IP Internet Protocol IoT Internetof Things lt Lifetime (CoRE Link Format attribute) M2MMachine-to-Machine NON Non-confirmable (CoAP message) RD ResourceDirectory RDID RD Identifier RFID Radio Frequency Identification rtResource Type (CoRE Link Format attribute) SP Service Provider URIUniform Resource Indicator

TABLE 2 Terminology Client An entity that uses the Lookup Interface ofan RD to search for CoRE Links that represent resources hosted byendpoints. Context The term refers to contact information an RD has foran endpoint or another RD. Typically, this comes in the form of an IPaddress and port number or an FQDN of the endpoint or RD duringregistration or update to a registration. CoRE Link According to IETFRFC 6690 Constrained RESTful Format Environments (CoRE) Link Format, aCoRE Link Format is a particular serialization of typed links based onthe HTTP Link Header field serialization defined in Section 5 of IETFRFC 5988 Web Linking, but carried as a resource representation with amedia type. In the context of RD, endpoints register the resources theyhost as CoRE Link Formats to an RD. Then clients search for theseresources and are provided the CoRE Links by the RD. Endpoint An IoTdevice that registers its resource URI(s) to a RD. It is defined by theIETF RD draft as, “an endpoint is used to describe a web server thatregisters resources to the Resource Directory. An endpoint is identifiedby its endpoint name, which is included during registration, and isunique within the associated domain of the registration.” Domain “In thecontext of a Resource Directory, a domain is a logical grouping ofendpoints. This specification assumes that the list of Domains supportedby an RD is pre- configured by that RD. When a domain is exported toDNS, the domain value equates to the DNS domain name.” See the IETF RDdraft. Geo-fence A virtual perimeter for a geographic area in the real-world. It may be specified as a geometric shape such as a circle or arectangle or some pre-set boundaries such as a neighborhood. Typically,GPS coordinates or RFID are used to define the boundaries. Extended Theprocess an RD undertakes to query other RDs for Searches CoRE Links thatmatch the search criteria of a client. These searches are enabled byRD-to-RD communica- tions. The querying RD of the extended search thenaggregates all responses together and returns the list of CoRE Links tothe client. RD-to-RD The process of an RD registering to another RD.Registration Registering An RD that is registering to another RD andprovides RD various metadata to enable RD-to-RD communications.Registrar An RD that accepts registrations from other RDs and RDendpoints. Resource “A web entity that stores information about web re-Directory sources and implements the REST interfaces defined in thisspecification for registration and lookup of those resources.” See theIETF RD draft. Typically, an RD is an “always on” node that isimplemented as a database to contain registration details of endpointsand the re- sources they host as CoRE Link Formats. RD may also containinformation about other RDs. Web According to RFC 6690, Web Linking is a“framework Linking for indicating the relationships between webresources.”

IETF RFC 7252 Constrained Application Protocol (CoAP) was designed foruse in IoT systems where devices have limited capabilities in terms ofCPU, RAM, ROM, etc. It offers functionality similar to the IETF RFC 2616Hypertext Transfer Protocol (HTTP) that is widely used in the Internetbut operates in a lightweight manner. These protocols provide forrequest-response mechanisms for two entities to communicate with eachother. Throughout the IETF RD draft, the messages transmitted between anendpoint or client to an RD are either formatted in CoAP or HTTPprotocol. The call flows in the figures include CoAP messages.

FIG. 1 provides some examples of message exchanges between a CoAP clientand a CoAP server. The first set of exchange shows a CoAP client sendinga non-confirmable (NON) request to the CoAP server targetingthe/temperature resource. A token is provided for matching responses torequests and a message ID ([0x7a11]) is used for detecting duplicatemessages. The CoAP server returns a NON response with the content of theresource, an appropriate response code (e.g. 2.05 Content), the tokenfrom the request, and a different message ID as it is a separatemessage. This set of message exchange is used when reliable transmissionis not required between the CoAP client and the CoAP server.

In the second set of message exchange, the CoAP client sends aconfirmable (CON) request and once again targets the/temperatureresource but using a different message ID. The CoAP server returns apiggy-backed response in which the content of the resource is combinedwith the acknowledgement to the confirmable request and an appropriateresponse code. This set of message exchange is used when reliabletransmission is required between the CoAP client and the CoAP server.

A third set of message exchange is shown in which the CoAP server is notable to immediately return a response to the CoAP client. In this case,the CoAP server returns an acknowledgement (ACK) response to the CoAPclient with the same message ID as the one provided in the request. Thenwhen the content of the resource is available, the CoAP server returns aCON response with the content of the resource, an appropriate responsecode, a different message ID, and the token provided in the request.

RFC 6690 CoRE Link Format was developed to describe the resources ofconstrained devices similar to how RFC 5988 Web Linking describes webresources. The purpose of these links is to provide for discovery of andaccess to those resources. As such, each link consists of a UniversalResource Identifier (URI) that locates the resource and some attributesthat further describe the resource. The Web Links are carried in theHTTP Link Header format of the associated resource while CoRE Links arecarried in the payload as resource representation. The links arediscovered through “Web Discovery” and CoRE Resource Discovery,respectively.

The IETF RD draft provides a centralized server where IoT endpoints mayregister their resources for discovery over a web interface. The salientfeatures of IoT endpoints (i.e. sleep-enabled devices and/or deviceslocated in disperse networks) make the discovery of their resourcesdifficult. Being a centralized server, the RD hosts the descriptions ofresources residing on various IoT endpoints and allows for clients tosearch the RD for those resources. As such, both registration and lookupinterfaces are defined to enable these functionalities. In addition, athird interface—group—provides the ability to combine endpoints intogroups. FIG. 2 shows the architecture of the CoRE RD.

If an endpoint is not provisioned with sufficient information tocommunicate to an RD, it may perform an RD Discovery method as shown inFIG. 3. The endpoint may multicast a GET message targeting the“/.well-known/core” URI. In the URI, the endpoint may include anoptional CoRE Link Format rt attribute, which indicates the type ofdiscovery it would like to perform. In this case, rt stands for ResourceType and may consist of one of the following values: “core.rd*”,“core.rd-lookup”, and “core.rd-group”. These values correspond to theinterfaces the RD supports. The “*” is a wildcard used to get the RD toreturn information for all its interfaces that match the preceding text.An RD will then respond with the contents of its interfaces and may alsoinclude hints on the content type it supports. These hints are includedas values of the ct CoRE Link Format attribute.

Once an endpoint discovers the RD, it may then proceed to register itsresources on the RD through the Registration Interface. FIG. 4 shows anendpoint registering to the RD. The endpoint sends a POST requesttargeting “/rd” and provides an endpoint name “node1”. In the payload,the endpoint includes a list of CoRE Link Formats corresponding to allthe resources the endpoint wants to register to the RD. The RD returnsan appropriate response to the request and if successful, the RD alsoincludes a location for the endpoint registration. This location is usedby the endpoint to update/delete its registration on/from the RD.

When an endpoint successfully registers to an RD, the RD keeps theregistration active for a certain period of time as defined by thelifetime attribute (lt). The lt attribute may be provided by theendpoint or it could be determined by the RD based on some defaultvalue. An endpoint must maintain its registration status by periodicallyrefreshing its registration information with the RD. Endpoints performthis as shown in FIG. 5. The endpoint performs a POST request towardsthe URI returned in the Location header of a successful registration.The RD returns a 2.04 Changed response to indicate a successful update.Besides updating its registration lifetime, an EP may also update itscontext information if its IP address or port number changes.

Similarly, EP registration removal is an explicit method in which anendpoint removes its registration information from the RD. FIG. 6 showsthis registration removal method and the RD response of 2.02 Deleted.

The RD also has an interface for performing lookup of the CoRE Links ithosts. A client may use the RD's Lookup Interface to query for the CoRELinks in which the client is interested. FIG. 7 shows an example of aclient querying for a CoRE Link with a resource type of temperature. Ifthere is a matching resource type, the RD returns the CoRE Link(s)corresponding to the resource(s). The client may then contact theendpoint to get the desired resource using information provided by theCoRE Link.

IETF RFC 6763 DNS-based Service Discovery specifies a mechanism forclients to discover resources using standard DNS queries. Typically,DNS-SD provides for coarse-grained discovery of an endpoint's IPaddress, port number, and protocol while RD provides for morefine-grained discovery of resources and their attributes. As such,DNS-SD and RD are complementary to each other and the RD resourcerecords are named and structured in such a way to facilitate servicediscovery. IETF RD draft defines a mapping between CoRE Link Formatattributes to DNS resource records so resources within the RD may bediscovered by using DNS-SD.

CoAP Observe, as described in IETF RFC 7641 Observing Resources in theConstrained Application Protocol (CoAP), is an extension of the CoAPprotocol to allow CoAP clients to get notifications for changes to aresource residing on a CoAP server. The CoAP client “observes” theresource by registering to the CoAP server using the GET methodtargeting the URI of the resource and setting the observe option equalto 0. Upon receiving the request, the CoAP server returns the content ofthe resource to the CoAP client. If the CoAP server accepts the observeregistration, it will include an Observe option in the form of asequence number in the initial GET response. This indicates to the CoAPclient the observe request was granted. Then, whenever a change of stateoccurs to the observed resource, the CoAP server will send anotification message to the CoAP client.

FIG. 8 shows a sequence of observe messages between a CoAP client and aCoAP server. Initially, the CoAP client sends a GET request targetingthe /temperature URI, a token 4 a, and the observe option value set to0. In response, the CoAP server returns a 2.05 Content response code,the same token 4 a, an observe sequence number 12, and the payloadcontent 22.9 Cel. The inclusion of the observe sequence number in theresponse indicates that the CoAP server has granted the CoAP client anobservation to the resource /temperature. Then a second notification issent by the CoAP server in response to a change in state of thetemperature resource. The response includes a new incremented observesequence number, the new content of the resource, and the token providedby the original observe registration request. The CoAP server continuesproviding notifications to the CoAP client whenever a change in stateoccurs to the resource until the observe request is cancelled using oneof the mechanisms defined in RFC 7641. Notice that the response code ofall the notify messages are 2.05 Content to indicate the content of theresource is provided in the payload.

FIG. 9 shows a smart city use case in which an RD is deployed indifferent areas of a city. The RDs host CoRE Link Formats of resourcesassociated with traffic and street lights, fire hydrants, and parkingmeters and garages. Within a city's limits, there may be tens tohundreds of RDs deployed depending on the size of the city. Each deviceregisters all its resources as CoRE Link Formats to a nearby RD andmanages the registrations using the RD's Registration Interface.

An RD client may then query other RDs using each RD's Lookup Interfaceto find the resources the client is looking for. The RD client currentlyneeds to query each RD separately if it wants to find a particular typeof resource in the whole city. For example, if a user (RD client) wantsto find all the parking garages in a certain part of the city, it firstneeds to locate all the RDs that serve that portion of the city and thenperform individual queries against those RDs. Furthermore, if a firemarshal wants to find all the fire hydrants throughout the city, thefire marshal would first need to discover all the RDs that service thecity and then perform individual queries. As stated before, there couldbe tens to hundreds of RDs deployed throughout the city limits.

The requirement of having the RD client discover and query each RD is aresult of a limitation in the IETF RD draft. This limitation existssince the RD specification lacks a mechanism for RDs to communicate witheach other. As a result, queries to an RD will only generate resultslimited to the CoRE Links that are hosted on that particular RD. In anIoT world where it is forecasted to include billions of devices, thislimitation cripples an RD's ability to locate remote IoT resources forthe clients it serves. End devices also suffer from a lack of exposuredue to the limited reach of the RDs.

When RDs are able to communicate with each other, they may communicateas peers or in a parent-child relationship as shown in FIG. 10. Thisclassification of parent-child or peer-to-peer is important duringRD-to-RD Registration when RD Identifiers (RDID) are exchanged. An RDclassified as a parent provides RDID management whereas peer RDs do nothave this functionality. In addition, a child or peer RD may providemore comprehensive results to client queries by utilizing parent RDsduring Extended Searches. The architecture offers flexibility instructured deployment scenarios whether in a top down or bottom upapproach that allows for easier management of the RDIDs. However, thearchitecture does not prevent ad-hoc deployments. In such instances,some features of RDID management may not be available, for example, butExtended Searches and other features may still apply.

To enable RD-to-RD communications, FIG. 11 shows the four main featuresthat are introduced or enhanced. First, the RD Discovery method isenhanced to provide a new RDID in the response to the discovery request.This enhancement indicates RD-to-RD communication is available and mayhelp a recipient RD decide which RD to register to. After discovery, theRDs may register to each other using the new RD-to-RD Registrationmethod, which varies depending on the RD classification (e.g. parent,child, or peer). Once RDs are registered to each other, they may provideenhancements to client lookup queries by expanding the scope of CoRELinks that could be returned to a client due to the added capability ofsearching additional RDs. The lookup query is enhanced through the useof new RD Query attributes to enable the new Extended Search capability.Finally, the results of the Extended Search may include RD Meta-datathat provide added context to the original lookup query.

Before RDs are able to communicate with each other, they must firstdiscover neighbor or remote RDs. To that end, an RD may perform an RDDiscovery method using the “./well-known/core” target URI as specifiedin FIG. 3. RD Discovery may be performed when an RD is first deployed,and the method may be performed periodically in order to discover newlydeployed RDs. In practice, other equivalent mechanisms may be invokedwhen an RD performs discovery. In order to enable RD-to-RDcommunication, RD Discovery methods may be enhanced by allowingrequesting RDs to provide RD Query attributes described in, e.g., inreference to FIG. 12, and receiving RDs are required to provide an RDIDin addition to other information required in an RD Discovery response.The inclusion of RD Query attributes allows a requesting RD to narrowthe search to a specific RD meeting its requirements. In addition, thereceiving RD may provide the requestor with meta-data such as geo-fencearea, load capacity, resource and endpoint types, and other informationthat may help the requestor (either RD or endpoint) decide which RD toregister to. The RDID is an identification mechanism that is required inRD-to-RD communication and will be described, e.g., in reference to FIG.13.

FIG. 12 shows the RD Discovery method with the new enhancements of theRD Query attributes in the discovery request and the inclusion of RDIDand RD Meta-data in the discovery response. When the RD Discoveryrequest is multicasted, the RDID may offer added information to help thequerying RD decide on which RD to register to. For example, FIG. 12shows RD3 multicasting the Discovery request and receiving two responsesfrom receiving RDs. The RDID of the receiving RDs indicate they sharethe same parent RD in a structured deployment. Further information maybe gleaned if a partial RDID was pre-provisioned to RD3, as described,e.g., in reference to FIG. 20. The RDID may indicate a parent, peer, orchild RD of the requesting RD depending on the architectural deploymentscenario. Using this information and the intended operation of therequesting RD, a decision may be made to decide which RD to register to.

The RD Discovery response may also apply to other discovery mechanismssuch as DNS-SD. In this case, a querying RD finds a registrar RD usingDNS-SD. The RDID and other RD Meta-data may be included as part of theDNS-SD TXT resource record, which offers additional information aboutthe RD. As a result, the information provided in an RD Discoveryresponse as shown in FIG. 12 is also provided by DNS-SD. Using DNS-SD, aquerying RD may locate RDs beyond its local service area that willfurther enhance the Extended Search capability, as described, e.g., inreference to FIG. 25.

A new attribute called the RDID may be used by RDs during RD Discoveryand RD-to-RD Registration, as described, e.g., in reference to FIGS.18-23. The RDID serves as an identifier that offers flexibility to theregistration methods. As a result, the use of the RDID allows for easieridentification provisioning and management in large deploymentscenarios. This RDID consists of a sequence of numbers delimited by thecharacter “.”, such as “1.2.3”. Alternatively for more complexdeployments, the elements of the RDID may include alphanumericcharacters. For example, a simple, structured deployment may be achievedin which only numbers are used. The RDID may be structured such that thefirst number is for service provider identification and subsequentnumbers represent the hierarchical deployment scenarios of the serviceprovider. FIG. 13 shows some examples of how RDIDs may be constructed.Using such a scheme will enable fewer conflicts with duplicate RDIDs.The RDID may be pre-provisioned during deployment by the RD owner orservice provider. It could also be partially provisioned with a prefixRDID or not provisioned at all—in both cases, the registrar RD willprovide the RDID suffix or the entire RDID respectively for a successfulRD registration.

The specific use of RDID may vary from one deployment scenario toanother. For example, the RDID may be explicitly defined by the RD'sowner or service provider. There is no restriction on whether an RD mayhave only one RDID. For example, an RD may have multiple RDIDs in ad-hocdeployments and the Registration Table described herein supports suchcases. In addition, the inclusion of the RDID in all RD-to-RDcommunications is meant to indicate this is a communication from an RDand enables all the features within the communications (e.g. RD Queryattributes, RD Meta-data, Extended Search, etc.), rather than from aclient or an endpoint. Structured deployments simplify RDID provisioningand management. When RDID is used in an ad-hoc manner, RDID provisioningand management increase in complexity and there may be more conflictswith duplicate RDID.

A new RD-to-RD Registration method allows RDs to register to each other.An RD will typically register to one or more RDs so Extended Search isenabled; however, it is not necessary or required for an RD to registerto all RDs that are discovered. The registration requires an RDID thatis provided by the registering RD to the registrar RD—an empty orincomplete RDID fulfills this requirement if the registering RD is achild RD. Additional information about the CoRE Links the registering RDhosts as well as its location information may also be provided for usein enhancing client queries, as described, e.g., in reference to FIGS.14-15. The RDID may be pre-provisioned during deployment or be obtainedfrom the registrar RD if the registering RD is going to be a child RD ofthe registrar RD.

FIG. 14 shows a generic RD-to-RD Registration method in which RD1 is theregistrar RD and RD2 is the registering RD. Values for some CoRE Linkattributes were omitted to reduce clutter in the diagram. In step 0, RD2either performs RD Discovery or is provided with RD1's contextinformation either through pre-provisioning or as a result of ServiceDiscovery via DNS-SD.

In step 1, RD2 performs a POST request using the target URI “/rd” or anappropriate URI returned by the targeted RD during RD Discovery.Alternatively, a PUT request could be used as well. Part of the requestcontains a mandatory “RDID” attribute with an RDID. Optionally, theendpoint type (et) may be set to “rd” to indicate this is an RD-to-RDcommunication. Additional information about the registration could alsobe provided such as the GPS coordinates of the registering RD, itsgeo-fenced coverage area, and the endpoint and/or resource types theregistering RD hosts. The attributes d, lt, and con are existing CoRELink attributes defined by IETF RD draft. Their values are not pertinentto the generic method and are included for completeness. Other CoRE Linkattributes may also be included to provide the registrar RD with as muchinformation about the registering RD as possible. This will enhance theregistrar RD's ability to better perform Extended Searches, asdescribed, e.g., in reference to FIG. 25.

In step 2, RD1 checks its local Registration Table for duplicate RDIDand makes a determination on the registration request. If there are noduplicates, RD1 adds the RDID provided in step 1 to its RegistrationTable.

In step 3, RD1 returns an appropriate response code based on results ofthe check performed in step 2. In addition, it may include extrameta-data like the ones provided by the registering RD in step 1. Thisexchange of meta-data about each RD may be used later to improve clientsearches and help decide which RD's to target for RD Extended Searchesas, as described, e.g., in reference to FIG. 25.

In step 4, RD2 adds an entry to its own Registration Table for RD1,indicating it is a parent RD if that is the case.

Within the registrar RD, a Registration Table is maintained that listsinformation of all registering RDs. The table contains informationprovided by the registering RDs such as rt, et, and ct CoRE Linkattributes and an example of what information is kept in this table isprovided in Table 3. Some fields in Table 3 are denoted by “ . . . ” forbrevity so the entire table may fit within the margins of the page. Inaddition, the table provides the parent RD the current RD is registeredto, as shown by entry #1. Entries 2 to 4 are child RDs of the current RDwhile entry 5 is a peer RD. The rest of the table provides CoRE LinkFormat attributes lt, rt, et, and ct along with a geo-fence coveragearea that the registering RD serves. This additional information will beused to enhance client searches to provide more comprehensive resultsthat existing RD does not provide.

TABLE 3 Registrar RD Registration Table Example Entry Life- ResourceEnd-point Content # RDID Context ParentRDID time (lt) Type (rt) Type(et) Type (ct) Geo-Fence area 1 1.2 — 1 <time> . . . , . . . , . . . . .. , . . . 0, 40, 41 <(gpsCoordinates), <radius> 2 1.2.1 <IP1> — <time> .. . , . . . . . . , . . . , . . . 0, 40 <. . . , . . . , . . . > 3 1.2.2<IP2> — <time> . . . , . . . , . . . . . . , . . . 0, 40, 41 <. . . , .. . , . . . > 4 1.2.3 <IP3> — <time> . . . , . . . . . . , . . . , 0, 40<. . . , . . . , . . . > 5 1.5 <IP4> 1 <time> . . . , . . . , . . . . .. , . . . , . . . 0, 40, 50 <. . . , . . . , . . . >

After receiving the RD-to-RD Registration request, the registrar RD willdetermine if the request may be granted based on the RDIDs in itsRegistration Table. If there is no RDID entry matching the one providedby the registering RD in the local RD Registration Table, the registrarRD may accept the registration and return the registering RD's RDID inthe response. This confirms the RDID was accepted and indicates asuccessful registration. In addition, the registrar RD may return theresource types (e.g. via a list of rt values) it hosts and a list ofneighbor RD's context information the registering RD may be interestedin registering to. The list of RD's context information is determined byentries in the Registration Table that matches attributes provided inthe registration request. For example, if GPS coordinates were provided,the registrar RD may find a match with an RD whose geo-fence area coversthe GPS coordinates of the registering RD.

A failed response is generated whenever the registrar RD is notaccepting new registrations or if the provided RDID matches an entry inthe local registration table. Various reasons for not accepting newregistrations could be maximum capacity reached, an RD policy on whichRDIDs to accept registration from, RDs having overlapping coverage ofthe same resource types, etc.

The registrar RD may provide one of the following responses for a failedregistration. First, the registrar RD may provide a registration failedresponse with an error code indicating the reason of failure. Someexample reasons include “Bad Request”, “Duplicate RDID”, and “ServiceUnavailable”.

Second, the registrar RD may provide a registration failed response withan error code and with a list of neighbor RDs, which may include peerand/or child RDs. The list of neighbor RDs may be used by theregistering RD to register to another RD.

Third, the registrar RD may provide a registration failed response witherror code and with a suggestion of a new RDID that is valid for a newregistration. The registrar RD is providing an RDID to the registeringRD for use in a new registration request that will be accepted. Theregistering RD may then use the suggested RDID in a new registrationmessage.

FIG. 15 shows a failed RD-to-RD registration response where a new RDIDis provided in step 3. Upon receiving the new RDID, RD2 generates a newregistration message using the new RDID and executes steps 4 to 7, whichis the same as steps 1 to 4 of FIG. 14.

Once an RD is registered to another RD, it is the responsibility of theregistered RD to inform the registrar RD of changes to the endpoint andresource types it hosts. Similar to how an endpoint updates itsregistration to an RD, a registered RD should perform a similar updateto the registrar RD. In the update, the registered RD should includechanges to the resource and endpoint types it currently is hosting andother CoRE Link attributes it provided during registration. In addition,the lifetime (it) and context (con) attributes of the registering RDmust be maintained so they do not expire or are different from what theregistering RD is using respectively. The update of the resource andendpoint types are less critical and may be updated in regular intervalsas opposed to when it happens in real time. The registrar RD in turncould report the updates to its registrar RD as well. FIG. 16 shows ageneric RD-to-RD Registration update method. Compared to FIG. 5,additional Link attributes (e.g. et, rt, and gps) are included in theregistration update request. As a result, RD1 updates registrationinformation it keeps on RD2 in its Registration Table as shown in step2.

The RD registration removal method follows exactly that of the endpointregistration removal method as shown in FIG. 6. FIG. 17 shows a genericRD registration removal method as well as the two actions that areperformed within each RD—1) corresponding registration entries areremoved, and 2) any corresponding observe entries are removed.

For many figures herein, some steps are not shown in order to moreclearly highlight the different registration mechanisms. All theregistration methods shown herein execute the same steps as those shownin FIG. 14 except that the processing step within each RD is not shownin the figures. In addition, there may be security implications with allthe registration methods provided. The security implications areespecially important when a parent RD registers to its child RDs in abottom up deployment (e.g. when a SP builds the RD network by firstdeploying lower level RDs and followed by one or more level of parentRDs—see FIG. 10). In those cases, a token could be provisioned in allchild RDs and the parent RD is required to provide the token duringregistration in order to register to the child RDs.

The registering RD may operate as a parent or a child of the registrarRD. When registering, the RD may have its RDID fully provisioned,partially provisioned, or not provisioned at all. The registrationrequest is the same in all the cases but the information provided andthe resulting behavior of the registrar RD is different. FIG. 18 showsthe Fully Provisioned RDID case in which RD2 is the child RD registeringto the parent RD, RD1. This case is prevalent when an SP controls RDdeployments and has total control over the provisioning of the RDID. RD2is provisioned with an RDID that is a child of RD1. Since the SPcontrols the RDID assignment, there should be no conflict and RD1 shouldreturn a successful registration with the same RDID as provided by RD2.

Similarly, a registering RD may be fully provisioned but is a parent RDof the registrar RD. FIG. 19 shows this case in which RD2 is a parent RDof RD3. The RDID provided in the registration request has the sameprefix as that of RD3's RDID and indicates that RD2 is the parent RD ofRD3. This scenario depicts the case where the SP deploys the RDs in abottom up manner, with the bottom being the child RDs.

There are cases where a fully provisioned RDID is not available ordesirable, e.g. RDID management for large systems. For these cases, theRD-to-RD registration method supports partially provisioned ornon-provisioned RDIDs. FIG. 20 shows a partially provisioned RDIDregistration in which the registering RD2 provides an RDID prefix thatmatches the registrar RD1's prefix. RD1 may be managing a large numberof RDs and upon receiving the partial RDID, RD1 may assign a suffix thatis not found in the local RD Registration Table. This combination of theprovided prefix and the assigned suffix would combine to form the entireRDID for the registration request. RD1 will then return the compositeRDID in the response to RD2.

Finally, a registering RD may provide an empty RDID to indicate it wantsto be assigned an RDID. Alternatively, the RDID could have an RDID valueof “.” instead as an indication of a request for RDID assignment. Thisapproach is the preferred mechanism in large scale deployments as theRDID is auto-provisioned and are dynamically managed by registrar RDs.The RDID may be determined by the entries of the local registrationtable in each registrar RD. FIG. 21 shows the case in which the RDID hasa “.” value for the RDID attribute in the registration request. When RD1receives such a request, it checks its local RD Registration Table tolocate an available RDID that is not present in the table. The new RDIDis added to the table and returned to RD2 to indicate a successfulregistration. Note the RDID returned should be a child RDID of theregistrar RD to avoid potential RDID conflicts in future registrations.The reason is the registrar RD doesn't have the insight into which peerRDID is available and it does not know which parent RDID is valid. Inad-hoc deployments, the registrar RD may return any RDID but it mayencounter RDID conflicts in the future as a result.

In a peer-to-peer scenario, the registering RD needs to provide anadditional attribute called the “pRDID” or Parent RDID. This newattribute denotes the parent RD of the registering RD and is used tolink the registering RD to its parent RD. Along with the parent RDID,the attribute also contains the context of the parent RD and as aresult, the pRDID attribute is a complex attribute. The registrar RD mayuse the information provided in the pRDID attribute to perform the newRDID Validation Query method specified below. The method allows theregistrar RD to verify with the parent RD (of the registering RD) theRDID provided by the registering RD. The inclusion of the pRDIDattribute will help the registrar RD resolve conflicts with duplicateRDID in future registrations.

FIG. 22 shows an example call flow for a peer-to-peer registrationrequest. This peer-to-peer RD-to-RD registration method includes an RDIDValidation Query process. The validation method helps minimize RDIDconflicts by having a third party validate the RDID of the registeringRD. Recall, a child RD may only have one parent RD. This is only asimple validation; for a more robust solution, security mechanismsshould be used instead. In this case, RD1 and RD2 have different parentRDs.

In step 0, RD1 and RD2 have different parent RDs.

In step 1, RD2 registers to RD1 and provides the pRDID attribute withthe RDID and context information of RD3, the parent RD of RD2. RD1obtains RD2's context information from the received message.

In step 2, using information from pRDID, RD1 performs the RDIDValidation Query and sends a GET request targeting RD3's rd-lookupinterface. Note the type of lookup is of type “rd” rather than thenormal res, et, and rt provided by IETF RD draft and this type indicatesan RDID validation query is being performed. In addition, RD1 provides anew attribute cRDID, which is the RDID of the child RD that is beingverified. If RD1 cannot reach RD3, RD1 may decide to either proceed withthe registration method or deny the request. This is left as animplementation policy for the design of RD1 and also may depend on thedeployment scenario. In a structured deployment, the policy may be todeny the request; whereas an ad-hoc deployment may allow theregistration.

In step 3, RD3 processes the GET request, locates RD2's registerinformation, and returns RD2's context in the response to RD1.

In step 4, RD1 validates RD2's registration by comparing RD2's contextfrom step 1 with that received from RD3 in step 3. Note, the requestfrom step 1 contains the context of the parent RD (RD3) in the pRDIDattribute. Furthermore, RD2's context information was obtained by RD1 instep 1. These two context information are different and representcontext of RD3 and RD2 respectively.

In step 5, RD1 sends an appropriate response to RD2 based on thevalidation result from step 4.

If an RD does not have a parent RDID, then the RD sends a null entry forthe pRDID attribute. This indicates that the registering RD is notregistered to another RD. As a result, there will be no conflict withRDID. However, the registrar RD still checks the local registrationtable for duplicate RDIDs to ensure the RDID is unique. This may occurif the RDID is incorrectly configured or in ad-hoc scenarios where theRDID is provisioned by a different user or SP.

In the event that the RD registers to a parent RD in the future, anupdate to the previous registration needs to be performed. FIG. 23 showsthe registration update method for this case. Initially, RD2 registersto RD1 without being registered to a parent RD. It provides its own RDIDand an empty pRDID. Upon receiving the registration request, RD1 noticesan empty pRDID attribute and hence it knows RD2 is not registered to anyother RD. As a result, RD1 only needs to check for duplicate RDIDagainst the ones in the local Registration Table. Sometime later, RD2registers to a parent RD. After the successful registration, RD2performs a registration update by using the POST method. This time, RD2provides the pRDID associated with the new parent RD. Alternatively, thepRDID attribute could also be placed in the payload of the message ifthere are other attributes that needs update, e.g. for an update of thelifetime of the registration as well.

In step 0, RD2 has no parent RD.

In step 1, RD2 performs a registration request, providing an RDID of1.2, an empty pRDID, and a list of resource types (rt) it hosts in thepayload.

In step 2, RD1 checks its local Registration Table for duplicate RDID,finds the RDID is available, and returns a success response.

In step 3, after some time, RD2 registers to a parent RD. This could betriggered by a parent RD registering to RD2 in a bottom up deployment.In this deployment scheme, child RDs are deployed first. Then as the RDbuildout progresses, parent RDs are deployed above the child RDs.

In step 4, RD2 then updates its registration on RD1 by providing thecontext of its parent RD.

In step 5, RD1 updates its Registration Table and sends an appropriateresponse to RD2.

Once RDs are registered to each other, existing RD lookups may beenhanced by having the receiving RD extend the search to all the RDs inits registration table, if necessary. The trigger of this ExtendedSearch will depend on the search parameters provided by the client. NewRD Query attributes allow clients to provide more criteria for enablingExtended Search. For example, if an RD client specifies a search forsome particular resource type within a geo-fence area, then thereceiving RD may extend the search based on the geo-fence area it has ofall registered RDs in its Registration Table. Furthermore, RDs involvedin the Extended Searches may provide RD Meta-data that provides moreinformation about the search and/or resources. The receiving RD willthen aggregate all search results together and return them to theclient. Finally, an RD may also provide mechanisms for caching CoRELinks of other RDs using an enhanced version of the CoAP Observefunctionality that are enabled due to RD-to-RD communications.

In the case an RD is heavily loaded and is not able to execute anExtended Search on behalf of the client, the RD may return the contextinformation of other RDs that contains Links the client is looking for.Then the client may issue another RD lookup query to the other RDs. FIG.24 shows such a case in which RD1 returns a 4.04 Not Found response codebut includes another RD's context information along with the associatedRDID. RD1 knows of RD2 as a result of RD2's registration to RD1.

When an RD client searches for CoRE Links of resources, an RD may nowexpand the search to include CoRE Links from other RDs that areregistered to it. A client may insert RD Query attributes to trigger theexpanded search, which is referred as an RD Extended Search. The RDQuery attributes provide additional parameters a client may use tospecify parameters for use in enhanced RD lookups. For example, if aclient provides the geo-fence area (gfa) attribute, the receiving RD mayuse this information and check against all registered RDs in itsRegistration Table to make a determination of which RDs to send theExtended Search. FIG. 25 shows an example of how the enhanced RD LookupQuery would work. The RD Extended Search provides clients the ability tospecify RD Query attributes in lookup requests and for RDs to return RDMeta-data in the lookup responses.

In step 0, RD1 and RD2 are registered with each other.

In step 1, an RD client performs an RD Lookup towards RD1 searching fora particular endpoint type that resides in a certain geo-fence area asspecified by the RD Query attribute gfa=[(gpsCoords1), (gpsCoords2),(gpsCoords3), (gpsCoords4)], which is a new search criteria for the RDLookup interface. In addition, other RD Query attributes could beincluded to direct the RD on what additional information is requested inthe response and how to extend the Extended Search. These may includethe number of RDs to search, whether to include the RDIDs associatedwith CoRE Links in the search response, an endpoint registrationlifetime cutoff, the number of levels of RD hierarchy to limit thesearch, a response time requirement, the number of CoRE Links to return,etc.

In step 2, using the information provided in its Registration Tablepertaining to geo-fencing, RD1 may identify RDs that fall within thegeo-fence area. Combined with other search parameters the client mayhave provided, RD1 creates a list of RDs with which to send ExtendedSearches to.

In step 3, using the list obtained in step 2, RD1 sends ExtendedSearches to all the RDs on the list. As part of the Extended Searchrequest, RD1 includes its own RDID with a set of RD Query attributesthat may or may not be the same ones provided by the client. Certain RDQuery attributes such as the geo-fence area are passed along in theExtended Search while other RD Query attributes such as the number ofCoRE Links to return are not passed along.

In step 4, RD2 returns the list of CoRE Links that matches the searchcriteria. In the response, RD2 may include RD Meta-data for the RD Queryattributes sent in step 3. This may include GPS coordinates of theendpoints, the remaining lifetime, etc. In addition, RDs should includethe RDID with the associate CoRE Links to identify where the Links arehosted in the responses. This will allow the Extended Search'saggregator RD the ability to identify duplicate CoRE Links and removethem before responding to the client.

In step 5, RD1 aggregates the responses from all the RDs with its ownlist of CoRE Links that meet the criteria of the original lookuprequest. In cases where the Extended Search produce results from thesame RD, RD1 may easily detect this by finding duplicate RDIDs and onlyaggregating the duplicates as a single set of results.

In step 6, RD1 returns the aggregated list of CoRE Links to the clientand may include any RD Meta-data that gives the client more informationabout the Links. The meta-data could include the GPS coordinates of theendpoints, the RDID of the RD that hosts the CoRE Links, etc.

Table 4 show examples of RD Query attributes that may be used by RDclients in performing enhanced RD lookups and the RD Meta-data thatcould be returned during Extended Searches. The table lists theattributes and meta-data that are applicable to the corresponding stepsoutlined in FIG. 25.

TABLE 4 Examples of RD Query Attributes and Meta-Data for used inExtended Searches Applicable in Meta-Data Step (Abbreviation)Description 1 3 4 6 RD Query Attributes numRD Limit the number of RDs inx performing Extended Searches numLinksLimit Limit the number of CoRELinks x that is returned in the response includeRDID Include the RDIDassociated with x CoRE Links in the response rspTimeReq Perform ExtendedSearch within x x the response time specified gfArea Geo-fence area x xgpsCoords GPS coordinates of the endpoints x x x where the x resourceresides regLTCutoff Registration lifetime cutoff speci- x x fies athreshold to limit the Ex- tended Search based on the remaining lifetimeof endpoint registrations. In other words, an RD should enable ExtendedSearch to return only the end- point registrations whose remaininglifetime is above the threshold provided. epAwake Limit search forendpoints that x x are awake RD Meta-data cacheResource A resource thatmay be cached at x a remote RD remainLT The remaining lifetime of the xx endpoint associated with the resource RDID The RDID of the RD thathosts x x the indicated endpoints associated with the resource. resCacheA cached copy of a resource x from another RD

As shown by Table 4, there are two types of RD Query attribute andanother two types of RD Meta-data. RD Query attributes are provided onan RD's Lookup Interface to provide finer grain search criteria. Thefirst type of RD Query attribute are attributes used between a clientand an RD, as shown by the Step 1 column in Table 4. The second type ofRD Query attributes are those used within RD-to-RD communications. Theseare provided by RD-to-RD during Extended Search. These are justcategories for the RD Query attributes and some may in fact beconsidered as both types. Similarly, there are two types of RD Meta-dataas well. The categories are similar to RD Query attributes: RD toclient, and RD-to-RD. The RD Meta-data provides contextual informationabout the results returned by an RD, whether it is for another RD or fora client.

A benefit of the parent-child architecture occurs during Extended Searchin which a child RD may forward a client query to a parent RD and letthe parent RD forward the requests to other child RDs. This mechanism isespecially useful whenever a comprehensive search is required and mayalso minimize latency in certain situations. For more time criticalqueries, the querying RD may want to communicate directly to its peerRDs to get responses as quickly as possible.

Through the course of operation, an RD may determine certain CoRE Linksare more popular than others by their presence in the aggregated resultsprovided to responses of multiple, but different queries. Alternatively,an RD may be presented the opportunity to store remote endpointregistration and their respective CoRE Links through the RD Meta-datacacheResource provided in the Extended Search responses. This meta-dataindicates that a CoRE Link may be cached on the receiving RD. An RD maythen initiate an unsolicited request to observe the CoRE Links byperforming an enhanced CoAP Observe as outlined in FIG. 26. In thiscase, RD1 is interested in observing CoRE Links on RD2 after a previousExtended Search showed the Links are cacheable. The RD is initiatingthis request not due to a client query but through its own determinationthat the Links are popular and the RD would like to cache a copy of theLinks in its local repository. The method is as follows.

In step 0, RD1 and RD2 are registered with each other.

In step 1, RD1 sends a GET request to RD2 with an Observe option and alist of CoRE Links in the payload that it is interested in observing.The GET request in this case is different than a typical Observe requestin that the target URI is not one of the observed resources. Rather, itis a typical RD client query targeting the RD Lookup Interface. The CoRELinks provided in the payload corresponds to the “resources” that therequestor wants to observe. Included in the request are RD1's RDID and atoken for the observation. The observe token in this case applies to therequesting RD and not to each observe resource. As a result, observedCoRE Links may be added or removed using the same token. Only when allthe CoRE Links associated with an RD are removed will the token beremoved. Various mechanisms could be used to indicate the enhancedObserve functionality: 1) the inclusion of an RDID, 2) the list of CoRELinks in the payload of the GET request, or 3) the addition of anenumeration to the Observe option.

In step 2, RD2 responds with the response code “2.05 Content”, thetoken, an Observe sequence number, and a list of endpoint registrationwith their respective CoRE Links that are observed. This specifies thatRD2 will notify RD1 of changes to the registration state of the endpointregistration and their CoRE Links.

In step 3, RD1 saves the CoRE Links listing provided by RD2.

In step 4, RD2 receives a request from an endpoint to updateregistration lifetime associated with the CoRE Link(s). This triggers anobserve event and requires RD2 to notify RD1 of the change to theregistration state of the CoRE Link(s).

In step 5, RD2 sends a notify message with the response code of “2.04Changed” along with the token, observe sequence number, and the changedCoRE Link(s). In normal Observe behavior, the notify message willcontain the response code “2.05 Content” instead. This is due to thefact that the original Observe functionality is interested in thecontents of a resource. The RD's use of Observe centers on the fact thatthe RD is interested in the registration state of the CoRE Link(s) andnot the contents of the CoRE Links. (If the contents of the CoRE Link(s)were to change, the normal Observe “2.05 Content” response code will besent.) As a result, the response code of an Observe notify message willbe used to indicate how the RD should treat the cached copy of the CoRELink(s). In this case, an update is required as the CoRE Linkregistration state has changed.

In step 6, RD1 updates the cached CoRE Link(s) provided by RD2.

In step 7, after some time, the endpoint deletes the CoRE Link(s) fromRD2. This triggers another observe event.

In step 8 a, RD2 sends another notify message but this time, theresponse code is “2.02 Deleted”. The response code reflects the factthat the CoRE Link(s) was (were) deleted in step 5.

In step 8 b, optionally, RD2 may proactively remove the observe entry ofany CoRE Link that is no longer being hosted. Alternatively, RD2 maywait for RD1 to cancel the observation either through a RESET message asshown in step 10 b or by an explicit Cancel Observe message as describedin RFC 7641.

In step 9, upon receiving the notify message from step 8 a, RD1 removesthe cached CoRE Link(s).

In step 10 a, optionally, RD1 may send a RST message to cancel theobservation.

In step 10 b, RD2 removes the observe entry.

Notice that the notify responses in steps 5 and 8 a are not the typical2.05 Content Observe response. The reason for this is the RD's use ofObserve is different than that of typical observe clients. Whereastypical observe clients are interested in the state of a resource (i.e.the value), RDs are interested in the registration state of the CoRELinks. This important distinction requires that the response codes foran RD observe should give the registration status of the CoRE Links. Asa result, 2.04 Changed and 2.02 Deleted responses are provided. Theresponse code in these cases will direct the receiving RD on how toprocess the cached CoRE Links.

New parameters, attributes, and meta-data described herein may be usedin both the Resource Directory communications outlined in RFC 6690 CoRELink as well as for new operations described herein, such as new RDQuery operations. New CoRE Link and RD Query attributes may be used tosupport RD-to-RD communications, for example. New RD Meta-data may bereturned during Extended Search operations.

The RDID attribute is an opaque string used to identify an RD as part ofRD-to-RD communications. The RDID consists of a sequence of numbersdelimited by the character “.”, such as “1.2.3”. For matching purposes,the entire string must be matched exactly on a per character basis. Onlyone value is allowed within the attribute and it must not appear morethan once in a link. The RDID may be fully provisioned, partiallyprovisioned, or not provisioned at all. In the latter two cases, theregistrar RD will provision the necessary components of the RDID to theregistering RD.

Similar to the RDID, the pRDID attribute is an opaque string thatidentifies an RD for RD-to-RD communications. The pRDID identifies an RDthat is the parent RD of the RD that presents this link attribute. Itfollows the same matching requirements, value multiplicity, and singleappearance in a link as the RDID. The pRDID is used in peer-to-peerRD-to-RD registration and is required for RDID validation. Theregistering RD provides the pRDID attribute when registering to a peerRD.

Similar to the RDID, the cRDID attribute is an opaque string thatidentifies an RD for RD-to-RD communications. The cRDID identifies an RDthat is the child RD of a parent RD indicated for RDID validation. Itfollows the same matching requirements, value multiplicity, and singleappearance in a link as the RDID. The cRDID is used in peer-to-peerRD-to-RD registration and is required for RDID validation. The registrarRD provides the cRDID attribute during RDID Validation Query method.

An RD client may provide a “number of RDs” (nrd) query attribute tolimit the number of RDs used for Extended Searches. A value of zeroindicates to the RD that the client only wish to query the local RD andthat Extended Searches should be disabled. A non-zero value indicatesthe number of RDs to include in the Extended Search. This attribute istypically used when an RD client is only interested in searchingsurrounding resources near the client.

An RD client may provide a “number of links limit” (nll) attribute tolimit the number of CoRE Links the RD returns. A client may not be ableto handle parsing a big list of results, or may not support CoAP blocktransfers. The nll attribute may be used when the search is targetedwith many query attributes and the client is expecting a small number ofresources to meet the search criteria. In those cases, the attributeprovides for a more comprehensive search while limiting the resultsreturned.

An RD client may provide an “include RDID” (iri) query attribute torequest that RDIDs be included in the response to a search. Depending onthe search results, the resource URIs may be found from multiple RDs. Asa result, multiple RDIDs may be included in the search response to theclient. This added information in the lookup response may help clientsbetter track the popularity of an RD in terms of resource URIs hosted.

An RD client may provide a “response time requirement” (rtr) queryattribute to limit the time an RD has in performing Extended Search. Thetime provided could either be an absolute or relative time and uponexpiration, the RD must return the search results to the client. Aclient will use this attribute to get timely responses and does not carethat the results are not comprehensive.

An RD client may provide a “geo-fence area” (gfa) query attribute tolimit an RD's search within the geo-fence area specified. The attributemay be complex. In Examples 1 and 2 below, the values are delimitedwithin square brackets. The ‘gfa’ attribute may also be considered aLink attribute. The attribute may consist of some combination of GPScoordinates and geometric shape to describe the area, e.g. circle,rectangle. Some examples are:

Example 1

-   -   Circle: gfa=[circle;<gpscenter>;<radius>]

Example 2

-   -   Rectangle: gfa=[rectangle; <gpstopLeft>; <gpsbottomLeft>;        <gpsbottomRight>; <gpstopRight>]

An RD client may provide a “registration lifetime cutoff” (rlc) queryattribute to selectively search an RD for resource URIs whose endpointhas a certain level of time remaining in its registration to an RD. Theattribute could contain either an absolute or relative time that isremaining on an endpoint's registration lifetime. This attribute may beused in cases where a client is looking to access the resource of anendpoint at a later time and wants to ensure the endpoint is stillavailable, for example.

An RD client may provide an “endpoint awake” (epa) query attribute toindicate to an RD to only search for resource URIs whose endpoints areawake up at s time specified in the attribute, for example. Theattribute could contain either an absolute or relative time that anendpoint is awake for. This attribute may be used in cases where aclient is looking to access the resource of an endpoint immediatelyafter getting the search response.

An RD may provide a “load capacity” (lc) meta-data in a response to anRD Discovery request to indicate the loading of the RD. Such meta-datamay include a percentage of the full capacity the RD have in terms ofhosting CoRE Links, for example. A higher percentage could indicate theRD is popular but also it is loaded and may incur longer processingdelays.

An RD may provide a “cache resource” (crs) meta-data during RD-to-RDcommunications to indicate resources it returns to another RD iscacheable. In return, an RD may need to perform RD Cacheable ResourceSynchronization method using enhanced Block Observe.

An RD may provide GPS coordinates (gps) meta-data during RD-to-RDcommunications to include location data of resources that are returnedin response to lookup requests. The values may be complex and consist ofGPS coordinates of the endpoint where the resource resides. Note thatthe gps' attribute may also be considered a Link attribute. Thismeta-data may be returned if the indicated resource falls within the‘gfa’ area specified by the lookup query, for example.

An RD may provide “remaining lifetime” (rlt) meta-data during RD-to-RDcommunications to provide remaining lifetimes of endpoints that host theindicated resources. This meta-data may be returned in response to the‘rlc’ Query attribute, for example.

An RD may provide a “resource cache” (rsc) meta-data during RD-to-RDcommunications for resource URIs that are cached copies of the originalresource URI residing in a different RD. This meta-data may be usefulespecially in the case when an RD client includes the ‘nrd’ queryattribute to limit the number of RDs queried for an extended search, forexample.

The following examples show some usage of the aforementioned attributesand meta-data. In the interest of brevity, some internal RD processingsteps may be omitted to highlight the salient features shown by eachexample.

FIG. 27 shows an example of a parent-child registration in which thechild RD, RD3, is registering to RD1 with an empty RDID attribute, i.e.no RDID is provided. In step 0, RD3 performs Service Discovery to locatethe context information of RD1. In step 1, using the context informationobtained from step 0, RD3 sends a registration request with the emptyRDID, its GPS coordinates, and the resource types (rt) RD3 hosts. Instep 2, RD1 then returns a 2.01 Created response with the assigned RDID1.2.2, a list of rt RD1 hosts, and another RD with the associatedcontext information that RD3 may be interested in registering to.

This case shows the streamlined registration mechanism of a parent-childregistration that could be used to deploy RDs in a large scaledeployment. The parent RD manages the RDID provisioning and provides fordynamic RD registration without the issue of RDID conflicts. RD ownersor service providers do not need to manage the pre-provisioning of RDIDfor the many RDs that are deployed.

FIG. 28 shows an example of the use of RD Extended Search enabled byRD-to-RD communications. In step 0, RD2 and RD3 both register to RD1,the parent RD. In step 1, a client performs an RD query to RD1 searchingfor the resource type (rt) “light”. In the query, the client specifiesthe iri and nrd attributes with values of 1 and 2 respectively. In thecase of iri, a value of 1 enables the inclusion of RDID in the resultsto the client query, while an nrd value of 2 specifies that the clientwants to limit the Extended Search to two RDs.

In step 2, RD1 searches its Registration Table for RDs that host the“light” resource type. Using the nrd value as a guide, RD1 selects the 2RDs matching the search criteria. If RD1 finds more RDs matching thesearch criteria than the nrd attribute, RD1 may still include the extraRDs in the Extended Search as to provide the most results to the clientand filter the results to limit them to two RDs, for example.

In steps 3 a and 3 b, RD1 sends an appropriate query to RD2 and RD3,respectively. Note that the nrd attribute is not included in therequests sent in steps 3 a and 3 b. This type of RD Query attribute isonly available on client queries, i.e. between a client and an RD. OtherRD Query attributes may also be used as part of attributes in theExtended Search, such as the gfa and the rtr attributes. The presence ofRDID indicates to RD2 and RD3 that this query is from an RD rather thana client.

In step 4, RD2 and RD3 return the results of the corresponding queriesin steps 4 a and 4 b. The results include the RDID of either RD2 or RD3as well as the list of CoRE Links that match the query criteria. Withineach CoRE Link, the crs attribute may be included for Links that arecacheable by RD1. This attribute is referred to as the RD Meta-data thatmay be returned by an RD's Lookup Interface. Within this type, there aretwo sub-types: ones that are provided in RD-to-RD communications (e.g.,crs) and others that are returned to the client (rsc). Once again, someRD Meta-data may be classified as both.

In step 5, once all the responses are received, RD1 aggregates theresults into a final report to send to the client. Included in thereport are results from searches from RD2 and RD3 as well as resultsfrom RD1 internally.

In step 6, depending on the RD Query attribute provided in step 1, RD1may need to format the report sent to the client. In this case, iri wasenabled and as a result, RD1 includes the RDID with the associated CoRELinks in the response. In the payload of the response, the Linksassociated with RD1 are listed first, followed by Links for RD2, andfinally, the Links for RD3. Note that the crs attribute is not part ofthe links. This is due to the fact crs is an RD-to-RD only meta-data.RD1 is informed by RDs 2 and 3 that certain Links are cacheable if thecrs attribute is set to 1. In the example, Links 1, 2, and 3 are able tobe cached by RD1 while Link 4 is not.

FIG. 29 shows another example of an Extended Search but this time, thesearch is spanned across multiple hops. The client in this case performsa query on RD3, which along with RD2 are child RDs of RD1, i.e. both RD2and RD3 are registered to RD1. In addition, RD3 is registered to RD4 aspeer RDs but RD3 is not registered to RD2. This example highlights thefact the Extended Search capability may span multiple hops while stillmeeting a response time requirement placed by the client using the rtrRD Query attribute.

In step 0, RD3 is registered to RD1 as a child RD and RD4 as a peer RD.RD2 is also registered to RD1 but RD2 and RD3 are not registered to eachother. RD4 is not registered to RD1.

In step 1, the Client performs a query for light resource type andspecifies a response time requirement (rtr RD Query attribute) for thequery.

In step 2, RD3 searches its Registration Table and makes a determinationto include RD1 and RD4 in the Extended Search.

In step 3 a, RD3 sends a GET request to RD4 with an rtr value that islower than the one provided by the client to account for processingdelays.

In step 3 b, RD4 is not able to expand the search to its child RDs andas a result, returns only the Links it hosts along with its RDID.

In step 4 a, RD3 sends another GET request to RD1 but with a larger rtrvalue as it is closer to RD1 than RD4. The rtr value may be calculatedbased on some algorithm programmed within the RD or through someempirical information obtained from previous communications.

In step 4 b, RD1 expands the Extended Search to include RD2 and forwardsthe GET request it receives but with a lower rtr value.

In step 4 c, RD2 returns a list of CoRE Links that matches the resourcetype light to RD1 along with its RDID.

In step 4 d, RD1 aggregates its own results with those received from RD2and returns them to RD3. The results are grouped according to RDID.

In step 5, RD3 aggregates the results from steps 3 b and 4 d with itsown results and send them to the client. If RD3 detects duplicate RDIDsfrom different responses, it may remove one set of CoRE Links from theresponse that is sent to the client. RD3 is filtering the results so theclient does not received duplicate CoRE Links.

FIG. 25 shows an example where the gfa RD Query attribute is used tolimit the search to a certain geo-fence area specified by “coords”, andthe gfa attribute is used to limit the RD Extended Search to only RDswithin a geo-fence area. The gfa query attribute is classified as bothclient to RD and RD-to-RD query attribute as it is used in both queries,as shown in steps 1 and 3. RD1 determines the RDs to include for step 3by comparing the given gfa to the information in its local RegistrationTable. In the example, only one RD, RD2, falls in the area specified bygfa and hence only one request is sent out for Extended Search. If RD2has an entry in its local Registration Table, it also may extend thesearch to include the RD associated with that entry. That is the benefitof allowing RD-to-RD communications—the search criteria may be enhancedto target a specific resource a client is looking for while getting alevel of comprehensive results.

As described in RFC 7641, the CoAP Observe functionality allows a CoAPclient to register to get notifications on changes to resources hostedby a CoAP server. The notification that is returned from the CoAP serverprovides data on the state of a resource and contains a “2.05 Content”code. In the context of RD communications, the Observe notification isenhanced to indicate an action to be performed on a cached CoRE Linkbased on the response code provided, as described, e.g., in reference toFIG. 26.

FIG. 26 outlines the usage of CoAP Observe from the perspective of RDcommunications. RD1 is interested in caching one or more CoRE Linksresiding in RD2 and performs an observe registration in step 1. Theinclusion of an RDID indicates to RD2 that the GET request is requestingthe enhanced Observe notifications, as described, e.g., in reference toFIG. 26. Alternatively, the presence of CoRE Links in the payload of theGET message may be used to indicate enhanced Observe notifications arerequested. Finally, a third alternative is to enumerate the Observeoption to request the enhanced notifications. The Observe option valuemay be modified as shown in Table 6-1.

TABLE 6-1 CoAP Observe Option Value Enumerations for EnhancedNotifications Observe Option Value Enumeration Description 0 Registeradds the entry to the list, if not present 1 Deregister removes theentry from the list, if present 2 (new) Register (for adds CoRE Link(s)to the list and enable enhance enhanced notifications notifications)

FIG. 30 shows an example of a new Observe functionality. The examplebuilds upon the example from FIG. 28 but only focuses on theinteractions between RD1 and RD2 and continues on after steps 1 to 6have been executed.

In step 0, RD2 and RD3 both registers to RD1, the parent RD. Note RD3 isnot shown in FIG. 30.

In steps 1-6, the method of FIG. 28 is executed. The important step forthis example is the return of the crs RD Meta-data in steps 4 a and 4 bof FIG. 28.

In step 7, RD1 performs an observe request on the cacheable Links 1 and2 by including them in the payload of an Observe request. Note the useof the new Observe registration mechanism as denoted by an Observe valueof 2. In addition, the token (tk) 1234 applies to both Links 1 and 2.

In step 8, RD2 creates an entry in its Observe table using the token1234 and adds Links 1 and 2 for RD1. All RD1 observe requests will usethis token; however, RD1 may also create another observe request with adifferent token. The use of multiple tokens by the same RD is useful forgrouping Links together. This is an implementation decision—a simplifyimplementation may limit only one observe token per RD while a morefeature rich implementation may allow multiple observe tokens for thesame RD.

In step 9, RD2 sends a 2.05 Content response to RD1 indicating theObserve request was granted. The same token as in the request and anobserve sequence number are provided in the response. Included in thepayload is the list of granted Links—the list may consist of all Linksin the request or a subset of the Links, e.g. if the observe table isfull when trying to add all the Links in the request, only Links thatwere successfully added are returned while Links not added are notincluded in the response.

In step 10, Link2 is updated.

In step 11, RD2 sends a 2.04 Changed notify message to RD1 with thecontents of Link2 in the payload. The same token and an incrementedobserve sequence number are included with the response. Note this iswhere the behavior of the Observe response is different from typicalObserve behavior—the response code indicates how RD1 needs to processthe information in the payload rather than merely providing the content.RD1 updates its cached copy of Link2.

In step 12, Link1 is removed.

In step 13, RD2 sends a 2.02 Deleted response to RD1 indicating the needfor removing the cached Link. Once again, the behavior here is differentthan existing Observe behavior. RD1 removes its cached copy of Link1.

FIG. 31 shows an example user interface of an RD Registration Table, asdescribed, e.g., in reference to Table 3. The user interface shows thelayout of RD interconnections and the registration relationships amongthe RDs. A user may touch one of the RD icons to select it and a dialogwindow pops up. Within the window, a heading shows what RDID isassociated with the selected RD. In addition, two GUI boxes show thestatus and configurations for the current RD. Finally, a table appearsat the bottom portion of the window that is similar to Table 3. Thetable shows the registration relationships between the selected RD andother remote RDs.

The various techniques described herein may be implemented in connectionwith hardware, firmware, software or, where appropriate, combinationsthereof. Such hardware, firmware, and software may reside in apparatuseslocated at various nodes of a communication network. The apparatuses mayoperate singly or in combination with each other to effect the methodsdescribed herein. As used herein, the terms “apparatus,” “networkapparatus,” “node,” “device,” and “network node” may be usedinterchangeably.

As shown in FIG. 32, the M2M/IoT/WoT communication system 10 may includethe Infrastructure Domain and the Field Domain. The InfrastructureDomain refers to the network side of the end-to-end M2M deployment, andthe Field Domain refers to the area networks, usually behind an M2Mgateway. The Field Domain and Infrastructure Domain may both comprise avariety of different nodes (e.g., servers, gateways, device, and thelike) of the network. For example, the Field Domain may include M2Mgateways 14 and devices 18. It will be appreciated that any number ofM2M gateway devices 14 and M2M devices 18 may be included in theM2M/IoT/WoT communication system 10 as desired. Each of the M2M gatewaydevices 14 and M2M devices 18 are configured to transmit and receivesignals, using communications circuitry, via the communication network12 or direct radio link. A M2M gateway 14 allows wireless M2M devices(e.g. cellular and non-cellular) as well as fixed network M2M devices(e.g., PLC) to communicate either through operator networks, such as thecommunication network 12 or direct radio link. For example, the M2Mdevices 18 may collect data and send the data, via the communicationnetwork 12 or direct radio link, to an M2M application 20 or other M2Mdevices 18. The M2M devices 18 may also receive data from the M2Mapplication 20 or an M2M device 18. Further, data and signals may besent to and received from the M2M application 20 via an M2M servicelayer 22, as described below. M2M devices 18 and gateways 14 maycommunicate via various networks including, cellular, WLAN, WPAN (e.g.,Zigbee, 6LoWPAN, Bluetooth), direct radio link, and wireline forexample. Exemplary M2M devices include, but are not limited to, tablets,smart phones, medical devices, temperature and weather monitors,connected cars, smart meters, game consoles, personal digitalassistants, health and fitness monitors, lights, thermostats,appliances, garage doors and other actuator-based devices, securitydevices, and smart outlets.

Referring to FIG. 33, the illustrated M2M service layer 22 in the fielddomain provides services for the M2M application 20, M2M gateways 14,and M2M devices 18 and the communication network 12. It will beunderstood that the M2M service layer 22 may communicate with any numberof M2M applications, M2M gateways 14, M2M devices 18, and communicationnetworks 12 as desired. The M2M service layer 22 may be implemented byone or more nodes of the network, which may comprise servers, computers,devices, or the like. The M2M service layer 22 provides servicecapabilities that apply to M2M devices 18, M2M gateways 14, and M2Mapplications 20. The functions of the M2M service layer 22 may beimplemented in a variety of ways, for example as a web server, in thecellular core network, in the cloud, etc.

Similar to the illustrated M2M service layer 22, there is the M2Mservice layer 22′ in the Infrastructure Domain. M2M service layer 22′provides services for the M2M application 20′ and the underlyingcommunication network 12′ in the infrastructure domain. M2M servicelayer 22′ also provides services for the M2M gateways 14 and M2M devices18 in the field domain. It will be understood that the M2M service layer22′ may communicate with any number of M2M applications, M2M gatewaysand M2M devices. The M2M service layer 22′ may interact with a servicelayer by a different service provider. The M2M service layer 22′ may beimplemented by one or more nodes of the network, which may compriseservers, computers, devices, virtual machines (e.g., cloudcomputing/storage farms, etc.) or the like.

Referring also to FIG. 33, the M2M service layers 22 and 22′ provide acore set of service delivery capabilities that diverse applications andverticals may leverage. These service capabilities enable M2Mapplications 20 and 20′ to interact with devices and perform functionssuch as data collection, data analysis, device management, security,billing, service/device discovery etc. Essentially, these servicecapabilities free the applications of the burden of implementing thesefunctionalities, thus simplifying application development and reducingcost and time to market. The service layers 22 and 22′ also enable M2Mapplications 20 and 20′ to communicate through various networks 12 and12′ in connection with the services that the service layers 22 and 22′provide.

The M2M applications 20 and 20′ may include applications in variousindustries such as, without limitation, transportation, health andwellness, connected home, energy management, asset tracking, andsecurity and surveillance. As mentioned above, the M2M service layer,running across the devices, gateways, servers and other nodes of thesystem, supports functions such as, for example, data collection, devicemanagement, security, billing, location tracking/geofencing,device/service discovery, and legacy systems integration, and providesthese functions as services to the M2M applications 20 and 20′.

Generally, a service layer, such as the service layers 22 and 22′illustrated in FIGS. 32 and 33, defines a software middleware layer thatsupports value-added service capabilities through a set of ApplicationProgramming Interfaces (APIs) and underlying networking interfaces. Boththe ETSI M2M and oneM2M architectures define a service layer. ETSI M2M'sservice layer is referred to as the Service Capability Layer (SCL). TheSCL may be implemented in a variety of different nodes of the ETSI M2Marchitecture. For example, an instance of the service layer may beimplemented within an M2M device (where it is referred to as a deviceSCL (DSCL)), a gateway (where it is referred to as a gateway SCL (GSCL))and/or a network node (where it is referred to as a network SCL (NSCL)).The oneM2M service layer supports a set of Common Service Functions(CSFs) (e.g., service capabilities). An instantiation of a set of one ormore particular types of CSFs is referred to as a Common Services Entity(CSE) which may be hosted on different types of network nodes (e.g.infrastructure node, middle node, application-specific node). The ThirdGeneration Partnership Project (3GPP) has also defined an architecturefor machine-type communications (MTC). In that architecture, the servicelayer and the service capabilities it provides are implemented as partof a Service Capability Server (SCS). Whether embodied in a DSCL, GSCL,or NSCL of the ETSI M2M architecture, in a Service Capability Server(SCS) of the 3GPP MTC architecture, in a CSF or CSE of the oneM2Marchitecture, or in some other node of a network, an instance of theservice layer may be implemented as a logical entity (e.g., software,computer-executable instructions, and the like) executing either on oneor more standalone nodes in the network, including servers, computers,and other computing devices or nodes, or as part of one or more existingnodes. As an example, an instance of a service layer or componentthereof may be implemented in the form of software running on a networknode (e.g., server, computer, gateway, device or the like) having thegeneral architecture illustrated in FIG. 34 or FIG. 35 described below.

For example, the service layer may be a functional layer within anetwork service architecture. Service layers are typically situatedabove the application protocol layer such as HTTP, CoAP or MQTT andprovide value added services to client applications. The service layeralso provides an interface to core networks at a lower resource layer,such as for example, a control layer and transport/access layer. Theservice layer supports multiple categories of (service) capabilities orfunctionalities including a service definition, service runtimeenablement, policy management, access control, and service clustering.Recently, several industry standards bodies, e.g., oneM2M, have beendeveloping M2M service layers to address the challenges associated withthe integration of M2M types of devices and applications intodeployments such as the Internet/Web, cellular, enterprise, and homenetworks. A M2M service layer may provide applications and/or variousdevices with access to a collection of or a set of the above mentionedcapabilities or functionalities, supported by the service layer, whichmay be referred to as a CSE or SCL. A few examples include but are notlimited to security, charging, data management, device management,discovery, provisioning, and connectivity management which may becommonly used by various applications. These capabilities orfunctionalities are made available to such various applications via APIswhich make use of message formats, resource structures and resourcerepresentations defined by the M2M service layer. The CSE or SCL is afunctional entity that may be implemented by hardware and/or softwareand that provides (service) capabilities or functionalities exposed tovarious applications and/or devices (i.e., functional interfaces betweensuch functional entities) in order for them to use such capabilities orfunctionalities.

Further, the methods and functionalities described herein may beimplemented as part of an M2M network that uses a Service OrientedArchitecture (SOA) and/or a Resource-Oriented Architecture (ROA) toaccess services.

FIG. 34 is a block diagram of an example hardware/software architectureof a node of a network, such as one of the devices illustrated in FIG.1-12 or 14-30, which may operate as an M2M server, gateway, device, orother node in an M2M network such as that illustrated in FIGS. 32 and33. As shown in FIG. 34, the node 30 may include a processor 32,non-removable memory 44, removable memory 46, a speaker/microphone 38, akeypad 40, a display, touchpad, and/or indicators 42, a power source 48,a global positioning system (GPS) chipset 50, and other peripherals 52.The node 30 may also include communication circuitry, such as atransceiver 34 and a transmit/receive element 36. It will be appreciatedthat the node 30 may include any sub-combination of the foregoingelements while remaining consistent with an embodiment. This node may bea node that implements aspects of the selective response to multicastrequests functionality described herein.

The processor 32 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. In general, the processor 32 may executecomputer-executable instructions stored in the memory (e.g., memory 44and/or memory 46) of the node in order to perform the various requiredfunctions of the node. For example, the processor 32 may perform signalcoding, data processing, power control, input/output processing, and/orany other functionality that enables the node 30 to operate in awireless or wired environment. The processor 32 may runapplication-layer programs (e.g., browsers) and/or radio access-layer(RAN) programs and/or other communications programs. The processor 32may also perform security operations such as authentication, securitykey agreement, and/or cryptographic operations, such as at theaccess-layer and/or application layer for example.

As shown in FIG. 34, the processor 32 is coupled to its communicationcircuitry (e.g., transceiver 34 and transmit/receive element 36). Theprocessor 32, through the execution of computer executable instructions,may control the communication circuitry in order to cause the node 30 tocommunicate with other nodes via the network to which it is connected.In particular, the processor 32 may control the communication circuitryin order to perform the transmitting and receiving steps describedherein, e.g., as described in reference to FIGS. 1, 3-8, and 11-30, andin the claims. While FIG. 34 depicts the processor 32 and thetransceiver 34 as separate components, it will be appreciated that theprocessor 32 and the transceiver 34 may be integrated together in anelectronic package or chip.

The transmit/receive element 36 may be configured to transmit signalsto, or receive signals from, other nodes, including M2M servers,gateways, device, and the like. For example, in an embodiment, thetransmit/receive element 36 may be an antenna configured to transmitand/or receive RF signals. The transmit/receive element 36 may supportvarious networks and air interfaces, such as WLAN, WPAN, cellular, andthe like. In an embodiment, the transmit/receive element 36 may be anemitter/detector configured to transmit and/or receive IR, UV, orvisible light signals, for example. In yet another embodiment, thetransmit/receive element 36 may be configured to transmit and receiveboth RF and light signals. It will be appreciated that thetransmit/receive element 36 may be configured to transmit and/or receiveany combination of wireless or wired signals.

In addition, although the transmit/receive element 36 is depicted inFIG. 34 as a single element, the node 30 may include any number oftransmit/receive elements 36. More specifically, the node 30 may employMIMO technology. Thus, in an embodiment, the node 30 may include two ormore transmit/receive elements 36 (e.g., multiple antennas) fortransmitting and receiving wireless signals.

The transceiver 34 may be configured to modulate the signals that are tobe transmitted by the transmit/receive element 36 and to demodulate thesignals that are received by the transmit/receive element 36. As notedabove, the node 30 may have multi-mode capabilities. Thus, thetransceiver 34 may include multiple transceivers for enabling the node30 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 32 may access information from, and store data in, anytype of suitable memory, such as the non-removable memory 44 and/or theremovable memory 46. For example, the processor 32 may store sessioncontext in its memory, as described above. The non-removable memory 44may include random-access memory (RAM), read-only memory (ROM), a harddisk, or any other type of memory storage device. The removable memory46 may include a subscriber identity module (SIM) card, a memory stick,a secure digital (SD) memory card, and the like. In other embodiments,the processor 32 may access information from, and store data in, memorythat is not physically located on the node 30, such as on a server or ahome computer. The processor 32 may be configured to control lightingpatterns, images, or colors on the display or indicators 42 to reflectthe status of an M2M service layer session migration or sharing or toobtain input from a user or display information to a user about thenode's session migration or sharing capabilities or settings. In anotherexample, the display may show information with regard to a sessionstate.

The processor 32 may receive power from the power source 48, and may beconfigured to distribute and/or control the power to the othercomponents in the node 30. The power source 48 may be any suitabledevice for powering the node 30. For example, the power source 48 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 32 may also be coupled to the GPS chipset 50, which isconfigured to provide location information (e.g., longitude andlatitude) regarding the current location of the node 30. It will beappreciated that the node 30 may acquire location information by way ofany suitable location-determination method while remaining consistentwith an embodiment.

The processor 32 may further be coupled to other peripherals 52, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 52 may include varioussensors such as an accelerometer, biometrics (e.g., finger print)sensors, an e-compass, a satellite transceiver, a sensor, a digitalcamera (for photographs or video), a universal serial bus (USB) port orother interconnect interfaces, a vibration device, a televisiontransceiver, a hands free headset, a Bluetooth® module, a frequencymodulated (FM) radio unit, a digital music player, a media player, avideo game player module, an Internet browser, and the like.

The node 30 may be embodied in other apparatuses or devices, such as asensor, consumer electronics, a wearable device such as a smart watch orsmart clothing, a medical or eHealth device, a robot, industrialequipment, a drone, a vehicle such as a car, truck, train, or airplane.The node 30 may connect to other components, modules, or systems of suchapparatuses or devices via one or more interconnect interfaces, such asan interconnect interface that may comprise one of the peripherals 52.

FIG. 35 is a block diagram of an exemplary computing system 90 which mayalso be used to implement one or more nodes of a network, such as thedevices illustrated in FIG. 1-12, or 14-30, which may operate as an M2Mserver, gateway, device, or other node in an M2M network such as thatillustrated in FIGS. 32 and 33. Computing system 90 may comprise acomputer or server and may be controlled primarily by computer readableinstructions, which may be in the form of software, wherever, or bywhatever means such software is stored or accessed. Such computerreadable instructions may be executed within a processor, such ascentral processing unit (CPU) 91, to cause computing system 90 to dowork. In many known workstations, servers, and personal computers,central processing unit 91 is implemented by a single-chip CPU called amicroprocessor. In other machines, the central processing unit 91 maycomprise multiple processors. Coprocessor 81 is an optional processor,distinct from main CPU 91, that performs additional functions or assistsCPU 91. CPU 91 and/or coprocessor 81 may receive, generate, and processdata related to the disclosed systems and methods for E2E M2M servicelayer sessions, such as selective response to multicast requests.

In operation, CPU 91 fetches, decodes, and executes instructions, andtransfers information to and from other resources via the computer'smain data-transfer path, system bus 80. Such a system bus connects thecomponents in computing system 90 and defines the medium for dataexchange. System bus 80 typically includes data lines for sending data,address lines for sending addresses, and control lines for sendinginterrupts and for operating the system bus. An example of such a systembus 80 is the PCI (Peripheral Component Interconnect) bus.

Memories coupled to system bus 80 include random access memory (RAM) 82and read only memory (ROM) 93. Such memories include circuitry thatallows information to be stored and retrieved. ROMs 93 generally containstored data that cannot easily be modified. Data stored in RAM 82 may beread or changed by CPU 91 or other hardware devices. Access to RAM 82and/or ROM 93 may be controlled by memory controller 92. Memorycontroller 92 may provide an address translation function thattranslates virtual addresses into physical addresses as instructions areexecuted. Memory controller 92 may also provide a memory protectionfunction that isolates processes within the system and isolates systemprocesses from user processes. Thus, a program running in a first modemay access only memory mapped by its own process virtual address space;it cannot access memory within another process's virtual address spaceunless memory sharing between the processes has been set up.

In addition, computing system 90 may contain peripherals controller 83responsible for communicating instructions from CPU 91 to peripherals,such as printer 94, keyboard 84, mouse 95, and disk drive 85.

Display 86, which is controlled by display controller 96, is used todisplay visual output generated by computing system 90. Such visualoutput may include text, graphics, animated graphics, and video. Display86 may be implemented with a CRT-based video display, an LCD-basedflat-panel display, gas plasma-based flat-panel display, or atouch-panel. Display controller 96 includes electronic componentsrequired to generate a video signal that is sent to display 86.

Further, computing system 90 may contain communication circuitry, suchas for example a network adaptor 97, that may be used to connectcomputing system 90 to an external communications network, such asnetwork 12 of FIG. 32 and FIG. 33, to enable the computing system 90 tocommunicate with other nodes of the network. The communicationcircuitry, alone or in combination with the CPU 91, may be used toperform the transmitting and receiving steps described herein, e.g., asdescribed in reference to FIGS. 1, 3-8, and 11-30 and in the claims.

It is understood that any or all of the systems, methods, and processesdescribed herein may be embodied in the form of computer executableinstructions (e.g., program code) stored on a computer-readable storagemedium. Such instructions, when executed by a machine, such as acomputer, server, M2M terminal device, M2M gateway device, or the like,perform and/or implement the systems, methods and processes describedherein. Specifically, any of the steps, operations or functionsdescribed above may be implemented in the form of such computerexecutable instructions. Computer readable storage media include bothvolatile and nonvolatile, removable and non-removable media implementedin any method or technology for storage of information, but suchcomputer readable storage media do not include signals. Computerreadable storage media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CDROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other physical medium that may be used to store the desiredinformation and that may be accessed by a computer.

In describing preferred embodiments of the subject matter of the presentdisclosure, as illustrated in the figures, specific terminology isemployed for the sake of clarity. The claimed subject matter, however,is not intended to be limited to the specific terminology so selected,and it is to be understood that each specific element includes alltechnical equivalents that operate in a similar manner to accomplish asimilar purpose.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A first apparatus comprising a processor, a memory, and communicationcircuitry, the apparatus being connected to a communications network viaits communication circuitry, the apparatus further comprisingcomputer-executable instructions stored in the memory of the apparatuswhich, when executed by the processor of the first apparatus, cause theapparatus to: implement a first resource directory; receive, from asecond resource directory, the second resource directory residing on asecond apparatus, a registration request comprising a resource directoryidentifier of the second resource directory; determine whether toregister the second resource directory based, at least in part, onresource directory identifier of the second resource directory and aregistration table; and register the second resource directory by addinga registration identifier of the second resource directory to theregistration table; and send, to the second resource directory, aresponse to the registration request.
 2. The first apparatus of claim 1,wherein the response to the registration request comprises a list ofregistered resource directories, or a list of available resources on oneor more resource directories.
 3. The first apparatus of claim 1, whereinthe computer-executable instructions further cause the first apparatusto create the registration identifier of the second resource directorybased, at least in part, on the resource directory identifier of thesecond resource directory.
 4. The first apparatus of claim 1, whereinthe registration request further comprises a resource directoryidentifier of a parent of the second resource directory, and wherein thecomputer-executable instructions further cause the first apparatus to:send, to the parent of the second resource directory, a request tovalidate the registration request; receive, from the parent of thesecond resource directory, a response to the request to validate theregistration request; determine, based, at least in part, on theresponse to the request to validate the registration request, or a lackof a response to validate the registration request, whether to registerthe second resource directory.
 5. The first apparatus of claim 1,wherein the computer-executable instructions further cause the firstapparatus to: receive, from the second resource directory, a resourcedirectory discovery query comprising one or more discovery queryattributes; determine whether to respond to the resource directorydiscovery query based, at least in part, on one of the discovery queryattributes; send, to the second resource directory, a response to theresource directory discovery query comprising a resource directoryidentifier of the first resource directory and resource directory data,where the resource directory data is related to one or more of thediscovery query attributes.
 6. The first apparatus of claim 5, whereinthe discovery query attribute include an attribute selected from thegroup consisting of a preferred resource directory identifier, aqualifier of resource directory identifiers, a limit on the number ofresource directories queried, a type of resource sought, a type ofendpoint served, a response time requirement, a geo-fence area, a set ofGPS coordinates, a registration lifetime cutoff, an endpoint awakerequirement, a loading capacity, a cache availability requirement, and aremaining lifetime requirement.
 7. A first apparatus comprising aprocessor, a memory, and communication circuitry, the apparatus beingconnected to a communications network via its communication circuitry,the apparatus further comprising computer-executable instructions storedin the memory of the apparatus which, when executed by the processor ofthe first apparatus, cause the apparatus to: implement a first resourcedirectory; maintain a registration table comprising resource directoryidentifiers for multiple resource directories and data regardingresources available at the multiple resource directories; receive, froma client, the client residing on a second apparatus and being anendpoint or a second resource directory, a request for a resource;determine whether the resource is available at one of the multipleresource directories by examination of the registration table; and ifthe resource is not available within the first resource directory but isavailable at one of the multiple resource directories, send a response,to the client, providing a resource directory identifier for a resourcedirectory having the resource.
 8. The first apparatus of claim 7,wherein the request for the resource comprises a query attribute, andwherein the computer-executable instructions further cause the firstapparatus to: maintain, within the registration table, data for themultiple resource directories pertinent to the query attribute; select asearch set comprising a portion of the multiple resource directoriesbased upon a match of the data to the query attribute; send, to thesearch set, a search query regarding the resource; receive, from a thirdresource directory, a first response to the search query; compose aresponse to the request for the resource based, at least in part, on thefirst response to the search query; and send, to the client, theresponse to the request for the resource.
 9. The first apparatus ofclaim 8, wherein the query attribute is selected from the groupconsisting of a preferred resource directory identifier, a qualifier ofresource directory identifiers, a limit on the number of resourcedirectories queried, a type of resource sought, a type of endpointserved, a response time requirement, a geo-fence area, a set of GPScoordinates, a registration lifetime cutoff, an endpoint awakerequirement, a loading capacity, a cache availability requirement, and aremaining lifetime requirement.
 10. The first apparatus of claim 8,wherein the computer-executable instructions further cause the firstapparatus to: receive, from a fourth resource directory, a secondresponse to the search query; and include, in the response to therequest for the resource based, information derived from the secondresponse to the search query.
 11. A method for communications amongresource directories, comprising: receiving, by a first resourcedirectory from a second resource directory, a resource directorydiscovery query comprising one or more discovery query attributes;determining, by the first resource directory, whether to respond to theresource directory discovery query based, at least in part, on one ofthe discovery query attributes; sending, to the second resourcedirectory, a response to the resource directory discovery querycomprising a resource directory identifier of the first resourcedirectory and resource directory data, where the resource directory datais related to one or more of the discovery query attributes.
 12. Themethod of claim 11, wherein the discovery query attribute include anattribute selected from the group consisting of a preferred resourcedirectory identifier, a qualifier of resource directory identifiers, alimit on the number of resource directories queried, a type of resourcesought, a type of endpoint served, a response time requirement, ageo-fence area, a set of GPS coordinates, a registration lifetimecutoff, an endpoint awake requirement, a loading capacity, a cacheavailability requirement, and a remaining lifetime requirement.
 13. Themethod of claim 11, further comprising: receiving, by the first resourcedirectory from the second resource directory, a registration requestcomprising a resource directory identifier of the second resourcedirectory; determining, by the first resource directory, whether toregister the second resource directory based, at least in part, onresource directory identifier of the second resource directory and aregistration table; and registering, by the first resource directory,the second resource directory by adding a registration identifier of thesecond resource directory to the registration table; and sending, thefirst resource directory to the second resource directory, a response tothe registration request.
 14. The method of claim 13, wherein theresponse to the registration request comprises a list of registeredresource directories, or a list of available resources on one or moreresource directories.
 15. The method of claim 13, wherein thecomputer-executable instructions further cause the first apparatus tocreate the registration identifier of the second resource directorybased, at least in part, on the resource directory identifier of thesecond resource directory.
 16. The method of claim 13, wherein theregistration request further comprises a resource directory identifierof a parent of the second resource directory, the method furthercomprising: sending, from the first resource directory to the parent ofthe second resource directory, a request to validate the registrationrequest; receiving, by the first resource directory from the parent ofthe second resource directory, a response to the request to validate theregistration request; determining, by the first resource directorybased, at least in part, on the response to the request to validate theregistration request, or a lack of a response to validate theregistration request, whether to register the second resource directory.17. The method of claim 13, further comprising: maintaining, by thefirst resource directory, a registration table comprising resourcedirectory identifiers for multiple resource directories and dataregarding resources available at the multiple resource directories;receive, by the first resource directory from a client, the client beingan endpoint or a third resource directory, a request for a resource;determining, by the first resource directory, whether the resource isavailable at one of the multiple resource directories by examination ofthe registration table; and if the resource is not available within thefirst resource directory but is available at one of the multipleresource directories, sending, by the first resource directory to theclient, a response providing a resource directory identifier for afourth resource directory having the resource.
 18. The method of claim17, wherein the request for the resource comprises a query attribute,the method further comprising: maintaining, by the first resourcedirectory within the registration table, data for the multiple resourcedirectories pertinent to the query attribute; selecting, by the firstresource directory, a search set comprising a portion of the multipleresource directories based upon a match of the data to the queryattribute; sending, by the first resource directory, to the search set,a search query regarding the resource; receiving, by the first resourcedirectory, from a third resource directory, a first response to thesearch query; composing, by the first resource directory, a response tothe request for the resource based, at least in part, on the firstresponse to the search query; and sending, by the first resourcedirectory to the client, the response to the request for the resource.19. The method of claim 18, wherein the query attribute is selected fromthe group consisting of a preferred resource directory identifier, aqualifier of resource directory identifiers, a limit on the number ofresource directories queried, a type of resource sought, a type ofendpoint served, a response time requirement, a geo-fence area, a set ofGPS coordinates, a registration lifetime cutoff, an endpoint awakerequirement, a loading capacity, a cache availability requirement, and aremaining lifetime requirement.
 20. The method of claim 18, furthercomprising: receiving, by the first resource directory from a fourthresource directory, a second response to the search query; andincluding, by the first resource directory, in the response to therequest for the resource based, information derived from the secondresponse to the search query.